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Author Topic: Antenna question  (Read 1236 times)
W0ALE
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Posts: 37




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« on: May 13, 2013, 08:20:32 PM »

I don't have an antenna mounted in my company truck, so I've been using my handhelds (a Baofeng UV-3R with stock and later Nagoya NA-701) Baofeng UV-5R with stock antenna with great results in the past.  I just bought a Kenwood TH-D72A and it has a Smiley 270A on it.  I don't have the stock antenna for it.  I have horrible noise coming through the radio from the engine (when I push the accelerator) with that antenna and have not had any issue with of the other radios or antennas.  I'm wondering if I got a bad antenna or if that one is just more sensitive or something.

I have a N9TAX Slim Jim that I've also hung in the back of the truck near the window that I've used with the Baofengs great results...just waiting on a pigtail to arrive that fits onto the Kenwood.

The rcv audio on the $50 UV-5R sounds a lot better when sitting side by side with the $400 Kenwood in my shack...I'm a little disappointed by that.  I'm hoping it's just an antenna issue.  The Kenwood transmits a lot better...no modulation issues like the UV-5R.
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WD8KNI
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« Reply #1 on: May 14, 2013, 02:31:31 AM »

Are any of the radios connected to the truck power supply?  If so unplug the power supply to find out if the noise is coming from the truck power.  If you find this is the case how old is the battery in the truck.  I have found that as batteries get old they don't have the filtering capability of new ones.  If the noise is there when on internal radio batteries, you have noise coming from the motor.

This is NOT an antenna issue.  a higher gain antenna will pick up more noise than a lower gain one.

Fred
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W0ALE
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« Reply #2 on: May 14, 2013, 06:15:27 AM »

Not connected to truck power... just on battery.   Maybe I'll just get a mag mount of the Slim Jim doesn't work.

That should have more gain than the HT antenna, right?  Just asking as I never had motor noise when using that with the Chinese HTs...
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K5LXP
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« Reply #3 on: May 14, 2013, 06:16:12 AM »

With all the computers in vehicles these days there is all manner of EMI/RFI that can radiate from the electronics and wiring.  The digital instrument cluster in my car is a fairly strong noise generator.  What I would try is an external antenna.  Even a mag mount would be better than any antenna inside the vehicle both in terms of reducing interference, and increasing 2M/440 performance.


Mark K5LXP
Albuquerque, NM
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W0ALE
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Posts: 37




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« Reply #4 on: May 14, 2013, 06:32:46 AM »

It's an old 89 Toyota pickup so not a lot of electronics.  I'll try the Slim Jim and a mag mount if that doesn't work.
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K5LXP
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« Reply #5 on: May 14, 2013, 06:51:31 AM »

It's an old 89 Toyota pickup so not a lot of electronics. 

Apparently something's in there - "  I have horrible noise coming through the radio from the engine (when I push the accelerator)"

That year is well past the point OBD I was implemented, so there's a computer in there somewhere.

Try different antenna combinations and see.  Easy/cheap enough to do.  An external antenna adds separation distance and the body will help act as a shield.


Mark K5LXP
Albuquerque, NM
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KC4MOP
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Posts: 731




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« Reply #6 on: May 14, 2013, 07:22:31 AM »

The injectors may be causing your problem.
I had a Toyota pickemup and the injector noise wiped out 17M HF. I found the wire that grounded all of the leads for the injectors and connected to another part of the engine. Noise went from S-9 to S-1 and then I could enjoy 17M. Apparently the grounding, even though it was originally connected to the engine block, was not good enough. I just experimented until the roar of noise disappeared.
Another problem for your situation may be the alternator. That's usually a whinning sound. The injectors will be a steady hash and will get worse as you rev up the engine.
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